1. Technical Field of the Invention
The present invention relates to an apparatus and a method for inspecting a sensor module mounted on a vehicle and the like that detects acceleration and angular velocity of the vehicle.
2. Related Art
Conventionally, an acceleration sensor (referred to, hereinafter, as a G sensor) that detects acceleration in the direction of an axis (referred to, hereinafter, as a detection axis) is installed in a vehicle. The G sensor is used to actualize a navigation function and an anti-lock braking system (ABS) function of the vehicle by providing information regarding acceleration in the longitudinal direction of the vehicle to a vehicle control unit.
To ensure detection accuracy of the G sensor described above, a method (referred to, hereinafter, as a sensor inspection method) is known in which characteristics of the G sensor are inspected using gravitational acceleration G1 of the Earth (refer to, for example, Japanese Patent Laid-open Publication No. Heisei 3-216557). In the method, a G sensor is placed on a reference surface of which sufficient horizontalness is ensured by a level. The G sensor is placed such that the detection axis thereof is perpendicular to the reference surface. An output voltage is then measured. Next, the G sensor is rotated by 90° from this state, and an output voltage is similarly measured.
However, in the above-described conventional sensor inspection method, when the G sensor is placed on the reference surface, the axis perpendicular to the reference surface is required to be precisely aligned in the direction of the gravitational acceleration G1 of the Earth. In other words, a process for aligning the axis is required. Therefore, the inspection requires extra time and effort.
In recent years, the number of functions (for example, a skidding suppressing function and an automatic cruise function) included in a vehicle has been increasing. Under the circumstances, in addition to a G sensor that detects acceleration by using a detection axis in the longitudinal direction of the vehicle (referred to, hereinafter, as a longitudinal G sensor), a G sensor that detects acceleration by using a detection axis in the transverse direction of the vehicle (referred to, hereinafter as a transverse G sensor), a yaw sensor that detects angular velocity around a detection axis in the vertical direction of the vehicle, and the like are used.
To shorten assembly time in a manufacturing process of the vehicle and reduce the number of defects during the assembly, so-called modularization is performed. The modularization integrates electronic components, a plurality of sensors, and the like used to actualize various vehicle functions into a package.
Therefore, ultimately, the characteristics of each sensor are required to be measured in a state in which a plurality of sensors and the like are integrated into a package (referred to, hereinafter, as a sensor module), and the sensor module itself is required to be inspected.
However, in the conventional sensor inspection method, to handle so-called modularization of the sensors described above, size of an inspection apparatus is required to correspond to the increased size (increased weight) of the package. In addition, axis alignment of the reference surface of the heavy inspection apparatus is required to be precisely performed in a state in which the heavy sensor module is placed on the reference surface. Therefore, the inspection requires further extra time and effort.